(40b) Understanding Powder Dissolution Performance through Particle Shape Characterization

In the food and pharmaceutical industries, products are often found in powder form to improve shelf life and transportation abilities, and then later reconstituted with water before end use. It is generally accepted that particle shape affects powder dissolution properties, but comprehensive research on the extent of these effects is lacking. In this study, 7 powder samples in two ingredient categories, proteins and sweeteners, are studied to determine the effects of particle shape on dissolution, and if these trends are similar across ingredient categories. The samples are sieved to 180-300 µm to minimize the effect of particle size variations. To study dissolution kinetics, 5.00 g of powder is dissolved in 100.0 mL of ultrapure water in a 250 mL beaker, stirred at 450 rpm using a magnetic stirrer and maintained at a temperature of 25 °C. An in-situ conductivity probe is used to track the change in conductivity during dissolution, which is used to measure the fraction of material dissolved in solution. The dissolution curve is then fit to the Weibull dissolution model to convey the dissolution rate constant. The dissolution properties are further studied using Dynamic Vapor Sorption (DVS) to determine the moisture sorption of powders at a given isotherm of 25 °C for sorption and desorption from 10% to 90% RH. The particle morphology of the powder samples is studied using the Malvern Morphologi G3SE-ID to obtain shape factors such as convexity and elliptical form factor (EFF). Particle size distributions and specific surface area at various stages in the dissolution process are determined using the Malvern Mastersizer 3000 and liquid dispersion unit. The results show that particles that are more convex and have a lower EFF (meaning a more irregular shape) have a higher dissolution rate. DVS results also suggest that more irregularly shaped particles can absorb more moisture in total, and start to adsorb moisture at a lower relative humidity. Therefore, particles that have greater shape irregularities tend to have greater dissolution performance.

This study aims to improve prediction of dissolution behavior through better understanding of the effect of particle morphology on powder ingredients. These findings can then in extension influence processing techniques to improve powder dissolution through control of particle shape. Ultimately, the results of this study would allow manufacturers to adjust the dissolution performance of products without adjusting processing parameters such as stirring rate or temperature.